Yesterday morning, when the seed was finally live and the servers had finally recovered, I updated (well, restored) my trusty two year-old iPhone 3GS to iOS 5 Beta 1. Since then I have made calls, sent messages, listened to music, tweeted, planned journeys and made journeys. This is a brief summary of what I've found.
Speed

It's no secret that the 3GS only just about copes with iOS 4. I certainly couldn't go back to version 3, but I do miss the snappiness that my phone had back then. Version 5 is pushing the ageing hardware even more, and this beta is just balancing on the usability line, occasionally falling off into a pit of hanging crashiness. Since there aren't really any new features that should really tax the hardware that iOS 4 didn't (apart from perhaps Notification Center) I'm going to put the rest down to this being an early beta, and that the bugs (and debugging code I assume is in there) are both to blame. If they're not, and the final release of iOS 5 on the 3GS is the same speed as this beta, it will be debatable whether this update is for all 3GS users.

Mail

I can flag mail! I can mark it as unread! And here's the best bit: weirdly formatted messages with tiny fonts and stupid forced line lengths get reformatted! No longer will I actually have to ignore someone's emails (there's a handful of people I know send mail like this – what is it that does it: Outlook, Blackberrys?) just because of the chore of sideways scrolling that was necessary to read their unholyl rich-text musings.

And also: on the train with horrendous 3G coverage, mail was failing to send. The status bar at the bottom detailed these unsent messages until they successfully wooshed off, with an extra little vibrate too! Good, good.

Twitter

If you use Twitter, you'll love the integration. if you don't, I doubt it's going to bother you. It would be nice if the tweet menu items get hidden if you don't install the Twitter client (I haven't test this but it would make sense).

I took a photo, and tweeted it straight from the camera app without switching to Twitter: it uploaded it using Twitter's new photo sharing service. I located myself on the map on a train to Manchester, and direct from there tweeted my location. It's not rocket science, but all good, and not switching apps is always a boon on older hardware, as this is where some of the biggest slow-downs can occur.

Maps

If you're in the UK, you'll have no doubt spotted the option to plan a journey by public transport, only to be disappointed that it never seems to find anything. Now it does! Now it finds ridiculous journeys for you that you'd never use! Baby steps though. And I've just bought the LJP app anyway.

Notifications

A better notification system was needed the moment push notifications were introduced and turned out to be A Really Good Thing. Even if you only call and text, the updated home screen view is a big improvement, and after that day out when you return to your phone that you left at home, you have a much more structured list of tiresome tasks to complete.

Camera

You can now use the shutter button to increase the ringer volume on your phone. Finally.

Widgets

Ok, so no-one at Apple has admitted it yet, but see Weather and Stocks in Notification Center? they're widgets they are, and there's no getting away from it: there's gonna be a whole set of apps asking if they can put a widget up there in six months time.

And a good thing too. I just wish I could get rid of the damned Stocks one: not even deleting every stock I track has removed it yet, it stubbornly stays, empty, acting like a massive 'go to Yahoo!' button.

Music

A subtle change here: no longer will you find an iPod app on your phone, instead you'll find the much more sensibly-named Music app. At the moment Apple get a new word accepted by the common tongue then they distance themselves from it like a self-conscience teenager huffing at his uncool dad who's trying to use the word 'brap' in conversation.

UI

Not much going on here really, although maybe I'm being unobservant. The switch control (UISwitch) has gone from rectangular to round (steady on, Apple). Oh, and in iTunes on the Mac, the volume control has been updated a bit to be more metallic and shiny.

Summary

There's a few biggies here that in another 24 hours I'll wonder how I ever did without (NC, Twitter, Mail flagging) and there's a big bunch of tiny things that have been fixed or improved that will keep me happy for weeks to come. The one big downside is the speed issue, but this is beta 1, and this is a two year old phone, filled to capacity (32GB of apps and data, I make Mail access 5 accounts totalling 7GB of data, 2 years of text messages...). It would be interesting to see if these sorts of things rally affect performance, I doubt they do very much (apart maybe for the SMS messages), I suspect that the beta-ness, the debug and the interaction between applications that really affects speed. This will be the main thing I'll be watching as we move through the beta versions, but I suspect my advice for any 3GS owners wondering whether to upgrade when the time comes will be a hearty 'yes'.

Addendum

You can argue the pros and cons of pushing a new OS to all your users ad infinitum, including where you draw the line (there were iPhone 1 owners upset they couldn't have iOS 4, iPhone 3G owners upset they had to have iOS4...). Indeed the entire area of upgrade cycles of both hardware and software, and support for those systems, is very difficult to get right – I personally think Apple are actually very good at treading the middle path on this one (and yes, I've been on the losing side sometimes). WIth iOS 5 though, Apple have introduced delta upgrades to the OS, which means they can have much more control of how far they push new features to older hardware, which should help to soften the edge of the ever approaching upgrade cliff.